MICROTAPER NEEDLE AND METHOD OF
CROSS-REFERENCE TO RELATED
This application claims the benefit of U.S. Provisional Patent Application No. 60/649,409, filed on Feb. 2,2005, and entitled "MICROTAPER NEEDLE", which is incorporated herein by reference in its entirety. 10
BACKGROUND OF THE INVENTION
1. The Field of the Invention
Exemplary embodiments of the invention relate to the field 15 of vascular access devices and methods. More particularly, the invention relates to apparatus and methods for efficiently obtaining vascular access in a manner that limits blood loss by patient.
2. The Relevant Technology 20 An important element in any medical procedure is the
control and reduction of blood lost by the subject (i.e. patient) of the procedure. Stopping blood loss is a particular concern in intravascular procedures where a laceration is made in a vein or artery so as to grant venous or arterial access. Com- 25 monly, these procedures involve the insertion, use, and removal of a guide wire, catheter, and/or other medical device to diagnose or attempt repair of a condition within the artery or vein. Intravascular procedures of this type represent a significant number of medical procedures performed each 30 year—well into the hundreds of thousands on human patients alone—thus providing at least an equal number of procedures where blood loss is a concern for human as well as animal patients.
Accessing a vein, artery or bodily cavity typically requires 35 entrance through a wall of the vein, artery or cavity (collectively referred to herein as "blood vessels" or "vessels"), which further requires that an access site be selected and the vessel wall be lacerated or punctured. The size of this access site is of particular concern. In general, the larger the access 40 site, the greater the amount of blood that may escape therefrom into the surrounding body cavities and tissue. Where excessive blood is lost, the effectiveness of the medical procedure may be compromised and complications may arise.
One method to avoid or reduce the risk of excess blood loss 45 is to reduce the size of the vascular access site. In a method commonly referred to as "micropuncture", a multi-step process is performed to give a physician vascular access through a small access site. Generally, the physician uses a 21 gauge (0.032 inch) hypodermic needle to access the blood vessel, 50 and a 0.018 inch guide wire is thereafter inserted into the vessel through the needle. With the guide wire in place, the needle may then be extracted from the vessel, leaving the guide wire in place.
Next, the physician places a coaxial dilator over the guide 55 wire and inserts the dilator into the patient's vessel. The vascular wall is flexible and resilient. Accordingly, as the dilator is inserted, the initial incision is stretched to accommodate the dilator. Thus, the dilator may have an outer diameter that exceeds the initial diameter of the access site, as well 60 as the needle used to make the access site. With the coaxial dilator in place, the guide wire and the inner dilator may be removed. The outer dilator has an internal diameter sufficient to accommodate a 0.035 inch guide wire which is then inserted. Upon insertion, the physician can then use the 65 inserted guide wire to insert and position a catheter in a patient's vasculature. Most commonly, the catheter has a
inner diameter of 0.035 inch or 0.038 inch. Once the procedure is complete, the catheter and guide wire may be removed. The access site in the vascular wall then returns to about its original size, thus reducing the patient's blood loss and recovery time.
While the micropuncture system provides vascular access in a manner that reduces blood loss and recovery time, it involves a variety of medical devices and procedures. For instance, as described above, the micropuncture system involves multiple steps and instruments. Accordingly, a need exists for devices and methods for obtaining vascular access with a reduced complexity and a reduced number of medical instruments.
BRIEF SUMMARY OF THE INVENTION
Exemplary embodiments of the invention relate to an apparatus and a method for accessing a blood vessel in a manner that limits the size of a corresponding vascular access site, while also allowing expansion of the vascular access site to receive larger medical devices such as guide wires and catheters. A needle with a tapered cutting end may create a vascular access site. Thereafter, a guide wire may be pushed through the needle and expand the tapered cutting end which temporarily stretches the vascular walls.
For example, in one embodiment, a needle of the present invention includes a substantially cylindrical tube formed along a central longitudinal axis. A tapered tube is connected to one end of the tube and has a sharpened end. A channel extends through the cylindrical tube and the tapered tube, and is aligned with the longitudinal axis. In some embodiments, the tapered portion is radially expandable. For instance, radial expansion may result when a guide wire is selectively inserted through the channel. The radial expansion may be facilitated by a relief on the tapered tube portion. Optionally, the relief includes a plurality of slots which expand as a guide wire is inserted through the channel and tapered portion, thereby also causing the internal and outer diameters of the tapered portion to expand.
In some additional embodiments, a medical needle comprises a substantially cylindrical tube and a tapered distal tube adjacent to and concentric with the cylindrical tube. Further, the medical needle may include a cutting tip at the distal end of the tapered tube, and a relief in the tapered tube for facilitating expansion of at least one diameter of the cutting tip. The outside diameter of the cylindrical tube may be greater than the outside diameter of the cutting tip. The relief may include one or more portions which, in some embodiments, are elongated slots formed in at least the tapered tube. One elongate slot may intersect a cutting surface of the cutting tip, while one or more additional slots may be offset from the cutting surface. The width of the slots can increase as a guide wire is inserted into the needle, and thus also deforming the tapered distal tube by increasing its outer and internal diameters.
In other embodiments, a method for inserting a medical device into a body cavity of a subject is described. A substantially tubular needle may be inserted into a body cavity and may have an internal passageway therethrough, as well as a sharpened distal end having a first internal diameter. A guide wire having an outer diameter greater than the first internal diameter may be inserted into the internal passageway. The sharpened distal end may be expanded to have a second internal diameter sufficient to allow the guide wire to pass through the sharpened distal end. Thereafter, the guide wire may be used to insert a medical device into a body cavity. Before the medical device is inserted, the needle may be optionally removed.